Unilateral Ankle Exoskeleton Assistance Reshapes Gait: Temporal Parameters, Load Distribution, and Inter-Limb...

Wearable exoskeletons have shown efficacy in gait rehabilitation and locomotor enhancement. Despite much work on the physiological and biomechanical aspects of human-exoskeleton interaction, systematic investigations into how exoskeleton assistance modulates gait parameters remain limited. This study investigated the effects of assistance timing and magnitude on gait parameters with a unilateral ankle exoskeleton. Twenty-two healthy participants completed nine personalized assistance profiles generated by combining three peak time settings and three peak torque levels. We analyzed temporal parameters (stride time, stance time, swing time, and stance ratio), vertical ground reaction force parameters (timing and magnitude of impact and propulsive peaks), and corresponding inter-limb symmetry indices. Moreover, we investigated the necessity of additional testing in reverse order and the influence of walking speed. Peak time significantly modulated most gait parameters, an effect amplified by higher torque. It affected most temporal parameters indirectly by modulating assisted stance time. Later peak time altered bilateral load-bearing by prolonging the assisted-limb single-support duration while shortening that of the unassisted limb and lowering its impact peak. Peak torque exhibited divergent influence trends on most gait parameters depending on peak time settings. Preliminary results indicated that additional reverse-order testing was unnecessary for these gait parameters. Walking speed had no significant effect on any symmetry index. These findings demonstrate that unilateral ankle exoskeleton assistance can strategically modulate gait parameters, redistribute lower-limb loading, and alter inter-limb symmetry, providing guidance for personalized gait training and assistance strategy design.